This invention pertains to locating the region of a power line transmission fault, and more specifically to systems to improve the efficiency and accuracy of locating the region of a power line transmission fault.
A Traveling Wave Fault Location (TWFL) time domain method for locating faults in power transmission lines is described in Gale, P. F., Stoke, J., Crossley, P. A., “Practical experience with traveling wave fault locators on Scottish Power's 275 & 400 kV transmission system”, Sixth International Conference on Developments in Power System Protection, 25-27 March 1997, Conference Publication No. 434, pp. 192-196. This method provides automated fault location determination and reporting. Additionally, physical separation of TWFL equipment from relay protection permitted compliance with current security requirements.
Disadvantageously, the TWFL time domain implementation requires highly accurate GPS time stamping of arriving traveling waves at the ends of the transmission line. Also, the performance of the TWFL time domain implementation is negatively affected by waves reflected from system elements adjacent to the faulted line, and by faults outside the monitored line. These problems occur because wave measurements must be performed when circuit breakers at both ends of the faulted power transmission line are still closed.
The prior art also describes a one-ended frequency domain voltage based traveling wave fault location method, where the distance to the fault is determined that the dominant frequency of a recovering voltage at the opened end of transmission line. See Ban, G., Prikler, L, and L., ‘Fault location on EHV lines based on electromagnetic transients’, IEEE/NTUA Athens Power Tech Conference “Planning, Operation and Control of Today's Electric Power Systems”, Athens, Greece, Sep. 5-8, 1993. Advantageously, this method does not require highly accurate GPS time stamping. Disadvantageously, however, simulation and field tests show that the method has limited accuracy. The precision of this one-ended fault location method depends on the accuracy of the value of the speed of wave propagation, v, along the faulted line. The velocity of propagation, v is affected by many factors, such as skin effect and ground resistivity along the power transmission line's corridor.
Therefore, there is a need for a more accurate system for locating the region of a power line transmission fault that does not depend upon the value of the speed of propagation, v.